For example, installation of a combustion pressure detecting device that detects the combustion pressure of an internal combustion engine on a device having the internal combustion engine, such as a vehicle, is under consideration. In such a device, based on the detection result of the combustion pressure by the combustion pressure detecting device, a controller called an ECU (Engine Control Unit) performs control related to operations or the like of the internal combustion engine.
For example, in Patent Document 1, it is described that a pressure detecting device incorporating a piezoelectric element that detects a combustion pressure of an internal combustion engine and a processing circuit that applies processing to detection signals of the piezoelectric element is connected to a controller that performs control based on output signals outputted from the processing circuit by use of an electric wire for supplying power from the controller to the pressure detecting device, an electric wire for transmitting signals from the pressure detecting device to the controller and an electric wire for making grounds of the controller and the pressure detecting device common.